It doesn’t provide a degree, charges no tuition, and offers only a training program in computer science. But after starting just two years ago, 42 has already shaken up how some here think about teaching, the value of credentials, and how best to prepare students for technology jobs. And it’s been wildly popular.

Some 70,000 people from Europe, the United States, and elsewhere applied last year for 900 openings, giving it an admissions rate lower than Harvard’s. Critics say its approach has few, if any, lessons for universities, and 42 lacks the state certification that’s required here to give it the imprimatur of legitimacy.

But Nicolas Sadirac, one of its four founders, says official accreditation is not what 42’s leaders aspire to — in fact, they shun it. “We don’t want to have to play by those rules,” says Mr. Sadirac, who describes France’s universities and vocational schools as lethargic knowledge factories that pump out rote learners.

“42’s goal is not to fill our students’ heads with facts and theories,” he says, “but to help them become creative innovators who can solve complex problems together with peers.”

In many ways, 42 resembles American companies, like General Assemblyand Codecademy, that have started in recent years to train people in computer coding and other skills while also questioning how well colleges prepare students for jobs. Like those efforts, 42 has its origins in the technology world.

It is the brainchild of Mr. Sadirac, 42’s director and a former university administrator, and the eccentric tycoon Xavier Niel, who made his fortune with Internet and telecommunications ventures. (A testament to Mr. Niel’s irreverence, which he flaunts, the school’s name comes from Douglas Adams’s novel The Hitchhiker’s Guide to the Galaxy, in which the number 42 is the key to all knowledge.) Mr. Niel put up about $90 million to set the project in motion in 2013. In addition to paying for its facilities, 1,000 iMacs, and a staff of 20, Mr. Niel’s donation supports each student. The school is tuition-free and meant to be accessible to young people from all backgrounds.

That idea isn’t radical in France, where public universities are highly subsidized and cost very little. But other aspects of 42 run opposite to the somewhat rigid education system here. The school has neither grades nor deadlines, diplomas nor books — not even a faculty.

For admissions, it ignores the baccalauréat, the test that essentially determines whether a student graduates high school and gets into college. Rather, applicants — anyone between 18 and 30 years old — take an online aptitude test, which if successfully completed lands them in a pool from which 4,000 are invited to 42’s home in northwestern Paris. The finalists are given a coding problem and four weeks to crack it. The project is rigorous — less than a quarter of them make the final cut.

No Professors, No Grades

The courses at 42 are run much like the entrance exam. In the place of classes, students choose projects (called piscines, or swimming pools) designed by 42’s staff with input from outside sources, including technology companies. Their task — and the way they learn — is to solve increasingly difficult problems working in teams of two to five. In the end, they either solve the problems and pass — or they don’t and fail. Students work at their own pace and are expected to “graduate” within two to four years.

All of this happens in 42’s sparse, industrial-sized halls with row after row of big-screen Macs. “It had been a business school,” says Mr. Sadirac with a smile, “but we ripped out all the classrooms.” If the all-nighters take their toll, there are cushions where students can sack out. For recreation there is table soccer as well as a computer game room.

Nicolas Sadirac directs the school, which is unaccredited and offers no degrees. “We don’t want to have to play by those rules,” he says.

Mr. Sadirac, a large man with a thick beard, explains that the aim of 42’s education is to put its programmers straight into France’s technology and software-engineering sector — which is short on highly skilled personnel — and thus to help France’s economy to better compete on a global level.

A key part of the 42 experience is an internship, usually in the fields of software development, telecommunications, or the Internet. Mr. Sadirac notes that 42’s go-getters are getting snapped up by those firms before they even finish the program.

“I love it,” says a second-year student, Laurie Mezard, who quit an undergraduate computer-science course in Paris before she took the 42 entrance exam. (Forty percent of the students who started in 2014 have never finished high school; others graduated from college, including elite universities like Stanford and Oxford.) “This isn’t really work,” she says. “It’s more like a game. You’re given challenges that are exciting to do.”

Since its inception, 42 has received a blizzardof press — overwhelmingly positive — as well as visits from representatives of mainstream tech-focused institutions, including Caltech and MIT. “A lot of institutions in France are taking on some of these ideas, like learning by doing instead of long, boring lectures,” says Olivier Rollot, a French journalist who writes about education.

A new film school in Paris, L’Ecole de la Cité, set up by the filmmaker Luc Besson, has dropped the admission criteria of a university degree, which is required by France’s other film schools. The University of Strasbourg has opened up a graduate program based on 42 in which computer-science students pursue their own projects without classroom instruction.

Yves Poilane, director of Telecom ParisTech, an engineering graduate school, says that 42 isn’t “a competitor but rather complementary to what we do. It takes in talented young people who didn’t fit into the system, for whatever reason. Usually they’d fall through the cracks.”

‘Boot Camp’

But how far 42’s ethos can be applied beyond its walls is a matter of dispute. Joel Courtois, managing director of the Paris-based EPITA Graduate School for Computer Science says that much of what 42 claims is new — the independent learning, internships in the professional world, even the swimming pools — has been in practice at EPITA since the 1980s.

Yet there are important differences, too. EPITA, like other programs recognized by the ministry of higher education, offers classes in ethics, foreign languages, social responsibility, and even mathematics and writing. “We also have to address the role of technology engineering in our society,” Mr. Courtois says, like by asking about “its impact, not just the most effective way to do it.”

Moreover, Mr. Courtois says that at state-certified schools a student doesn’t have to leave the program if he fails at a project. “We have faculty who help them learn how to do it,” he says. “We don’t want to destroy them.”

This year 42 scratched its initial deadlines for student projects. Some students told The Chronicle that new students were buckling under the pressure. (Mr. Sadirac says deadlines were done away with for technical reasons, not because of complaints, and are being reintroduced into the program gradually.)

The entrance exam and the first year have been described approvingly by Mr. Sadirac as “boot camp” and “grueling.”

“Not everybody is so motivated at the age of 18 to work like they’re in a start-up in Silicon Valley,” says Mr. Rollot, the journalist. “This can’t be the only option for those who don’t fit into the system.”

Critics also point out that 42 has very few women, just 8 to 10 percent of the student body. The 42 staff says that it does everything it can to recruit women but that computer sciences just don’t appeal to women in France. Other observers, who note that Mr. Niel’s online ventures have included pornography, say 42 could be trying harder to bring in women.

Mr. Courtois points out that students should have time to be students — like by participating in clubs, sports, and other extracurricular activities — none of which 42 offers. “They learn other skills that are important to build one’s own company,” he says.

“I don’t believe that education isn’t working in France. Of course all things can be improved,” says Mr. Courtois, responding to the critique that French higher education has grown stale. “But France already has good engineers. Facebook, Google, Microsoft — they all recruit our graduates and praise them highly. This means our system isn’t so bad.”